Significance There is a substantial amount of socially-induced stress associated with being HIV positive, arising from multiple sources, including discrimination, stigmatization, and experience of bereavements. The degree to which individuals experience such stress has been proposed as one factor contributing to the enormous variability in disease progress. Objectives Using the SIV-macaque model of HIV infection, we studied adult male rhesus macaques to determine whether having a stable social network is associated with a more favorable outcome following SIV inoculation than is having an unstable social network. Results Social stability was associated with fewer agonistic and more affiliative interactions than was social instability. Moreover, animals experiencing socially stable conditions survived significantly longer than did those experiencing social instability. We also discovered significant differences between stable and unstable animals in pituitary-adrenal functioning that may have mediated the effect between social condition and survival. Finally, examination of individual differences in behaviors displayed during the social groups revealed that animals that received aggressive behavior had higher viral loads than did animals that did not, regardless of which social condition they were in. These results clearly indicate that social instability has a negative impact on immunodeficiency disease outcome, and provides evidence that individual differences in coping are influential in explaining variation in SIV disease progression, even among socially-stressed individuals. Future Directions We intend to continue this research by examining the interaction of individual difference factors and social conditions on stress physiology and disease progression. KEYWORDS SIV, AIDS, psychosocial, stress, individual differences